Lecture 6- Population genetics II

Question 1

current environment of a gene

Answer 1

refers to the external world, and other parts of the genome the gene is part of

Question 2

difference between selection under single-locus vs quantitative models

Answer 2

for single loci, selection is either positive or negative, but for directional, it’s more about average trait value

Question 3

types of selection which can act on single loci

Answer 3

balancing selection, which favours coexistence of alleles

Question 4

how can change in gene frequency in single loci be expressed (haploid)

Answer 4

change in q = spq
where p and q are alleles
s is the change in fitness, e.g. 0.5 for 50% more fitness

Question 5

how does this calculation change for diploids

Answer 5

fitness is influenced by allele interactions, represented by degree of dominance (h)
change in q = spw[ph + q(1-h)]

Question 6

what can dominance do to phenotypic distribution

Answer 6

remove intermediates- e.g. pop becoming 75/25 something rather than 25/50/25- less fit allele can ‘hide’

Question 7

heterozygote advantage

Answer 7

when the heterozygous state is the best fitness-wise- e.g. in sickle cell, het gives advantage against malaria but homo rec means u get anaemia

Question 8

how would you look at multi-locus effects on phenotype

Answer 8

can see dominance from skews in graphs of phenotypes, therefore need a more phenotypic focus

Question 9

what types of selection can apply to a multi-locus trait

Answer 9

stabilising, directional, disruptive

Question 10

examples of areas of application for population genetics

Answer 10

breeding, conservation, e.g. UN convention on biological diversity (CBD)- aims to keep track of this, epidemiology, medical genetics